MySQL 获取物理表的主键字段

参考代码：

 /**
      * 获取主键字段
      * @param $table
      * @param $database
      * @return mixed
      */
     public function get_primary_key($table,$database){
         $sql = "SELECT
             k.column_name
         FROM
             information_schema.table_constraints t
         JOIN
             information_schema.key_column_usage k
         USING
             (constraint_name,table_schema,table_name)
         WHERE
             t.constraint_type='PRIMARY KEY'
         AND
             t.table_schema='$database'
         AND
             t.table_name='$table'";
         return Db::query($sql)[0]["column_name"];    // 数据库查询语句根据情况而定

     }